不同稳定化材料对废渣中As的固定效果

Stabilization effects of different materials on arsenic-containing slag

采用典型硫化物、钙基和铁铝基(Fe0、铁盐、Fe2O3/Al2O3)等共10种材料对含砷(As)废渣进行稳定化处理,通过5种模拟不同风险场景的单一化学浸提法,筛选出不同场景下固As效果好的材料,并通过连续化学形态浸提和微观结构表征揭示典型材料的固As机理.结果表明,自然场景下Na2S·9H2O固As效果最好,其它场景固As能力最强的依次是Fe0和FeSO4·7H2O,其中,Fe0最适用于有机弱酸和强酸雨场景,FeSO4·7H2O在5种场景中均有固As效果,但差异性较大,在有机弱酸场景下效果最好,TCLP浸出As降至1.50μg/L,固As率达99.98%.FeSO4·7H2O固As作用主要是降低弱酸可提取态,将非专性/专性吸附态、无定形和弱结晶铁铝或铁锰态转化为结晶铁铝或铁锰态和残渣态,处理后有少量难溶的铁砷矿物(即臭葱石和砷铁矿)等生成.

Ten kinds of typical materials including sulfides,calcium-based and iron-aluminum-based materials(Fe0,ferric salt,Fe2O3/Al2O3)were used to stabilize arsenic-containing slag.Five single chemical extraction methods simulating different exposure conditions were used to screen out materials with better stabilization effect.The mechanism underlying arsenic stabilization by typical materials was revealed by the analysis of continuous chemical extraction and microstructure characterization.The results demonstrated that Na2S·9H2O showed the best stabilization effect under natural condition.While,Fe0 exhibited the strongest arsenic stabilization ability followed by FeSO4·7H2O under other conditions.Fe0 is suitable for arsenic stabilization under organic weak acid and strong acid rain conditions.FeSO4·7H2O was effective under all conditions,however its effect varied greatly.It showed the best effect for arsenic stabilization under weak organic acid condition,and TCLP-As leaching was reduced to 1.50μg/L with arsenic stabilization rate of 99.98%.FeSO4·7H2O mainly reduced the extractable weak acid state,and converted the non-specific/specific adsorption state,amorphous and weak crystalline iron-aluminium or iron-manganese state into crystalline iron-aluminium or iron-manganese state and residue state.A small amount of insoluble iron and arsenic minerals(FeAsO4·2H2O and FeAsS)were formed after treatment.